This invention relates to methods and apparatii for establishing concurrent voice and non-voice communication between two remote sites. More particularly, this invention relates to full-duplex, concurrent voice/non-voice communication over the public switched telephone network (PSTN). To the end users, voice communication and data communication occur in real-time.
Concurrent voice and data communication is available in many environments, including the Integrated Services Digital Network (ISDN), private branch exchanges (PBX), satellite access protocols, and private LANs. Each of these environments enable high speed digital communication among end users. Each of these environments have grown as supplements and alternatives to communication over the public switching network (PSTN). None, however, completely replaces the PSTN for unrestricted telecommunication because of the extensive installation base of the PSTN. Typically, the alternative environments enable limited communication outside their environment (i.e., not the wealth of internal features within their special environment).
A shortcoming of the PSTN is its aging analog-based communication path. A strength of the PSTN is its large installation base, which enables communication to substantially anyone anywhere. While concurrent voice and data transmission within other environments is desirable and provides significant communication power, a system for concurrent voice and data communication over the PSTN is desirable.
Product technologies including concurrent voice and data communication include telewriting and video phone technology. Telewriting is a communication format in which image data consisting of characters and graphics is transmitted and received together with voice signals over a telephone line in real time. Typically the communication format conforms with telewriting standards established by the Consultative Committee in International Telegraphy and Telephony (CCITT) (i.e., "Telewriting Terminal Equipment", Consultative Committee for International Telegraph and Telephony (CCITT), Facsimile VII.5, Recommendation T.150, IXth Plenary Assembly, Melbourne, November 1988). Typically, telewriting is performed over PSTN lines, though it is an option in video conferencing systems which use high speed networks such as ISDN.
Video phones enable one to see another party while talking. High quality video phones typically operate on high speed data lines such as 64,000 bps or greater. AT&T announced a video phone which uses the ordinary PSTN line to send voice and `moving` images at 19,200 bps. The limitations of the PSTN line, however, result in a video image which is choppy and does not synchronize the voice with the speaker's movements.
ShareVision Technology Inc. of San Jose, Calif. announced a video-conferencing product for communication over a single ordinary PSTN line. Video-conferencing with still image capture capabilities, screen sharing and a fax-modem are specified. A proprietary compression algorithm is used to send and receive video images, voice and other data over a 14,400 bps modem connection. Users are said to have the ability to set priorities for voice and video, allowing them to trade slower image refreshes for better sound quality.
SPECOM Technologies Corporation of Santa Clara, Calif. markets a PICFON card for combining voice and picture communication over a single PSTN phone line. Picture data throughput is not fast enough for real time video phone imaging, yet is fast enough to display images while callers discuss the content. Such ability is useful for business meetings, remote presentations and telemarketing. Voice and data are full duplex at a bit rate up to 9600 bps (9600 bps data exchange during silence.) Communication is compatible with V.32 modem standards.